Control of allograft rejection by applying a novel nuclear factor-κB inhibitor, dehydroxymethylepoxyquinomicin

Background. Nuclear factor (NF)-kappa B plays a crucial role in lymphocyte activation, proliferation, and survival. We examined the immunosuppressive effect of a newly developed NF-kappa B inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ) in allotransplantation. Methods. Purified C57BL/6 (H-2(b)) T cells were used for in vitro studies examining activation, proliferation, cytokine production and nuclear NF-kappa B and nuclear factor of activated T cells (NFAT) protein levels. A fully major histocompatibility complex incompatible BALB/c (H-2(d))-to-C57BL/6 mice cardiac transplantation model was utilized for in vivo studies. DHMEQ was given intraperitoneally to transplant recipients at a various dose starting from day 0. In some, DHMEQ was administered concomitantly with tacrolimus. Results. DHMEQ significantly suppressed alpha CD3 + alpha CD28 monoclonal antibody-triggered T-cell proliferation, CD25/CD69 expressions, and both interleukin-2 and interferon (IFN)-gamma production in a dose-dependent fashion. DHMEQ blocked nuclear translocation of NF-kappa B but not NFAT in activated T cells. Combined treatment with DHMEQ and tacrolimus significantly suppressed T cell activation as compared to that of mono-therapy with either agent alone. Single DHMEQ treatment moderately prolonged cardiac allograft survival. Further, combination of DHMEQ plus tacrolimus markedly prolonged graft mean survival time (MST) to 59.5 days when compared to either DHMEQ (MST: 10 days) or tacrolimus (MST: 13 days) treatment alone. Such effect was associated with inhibition of mixed lymphocyte reaction against donor antigen, IFN-gamma producing splenocytes and graft cellular infiltration as examined at 5 and 12 days posttransplantation. Conclusion. DHMEQ inhibits nuclear translocation of NF-kappa B but not NFAT inactivated T cells, and prolongs allograft survival. Blocking both NF-kappa B and NFAT by DHMEQ and tacrolimus induces potent immunosuppression, which may become a new modality in controlling allograft rejection.